Symptoms

You're trying to add additional subnet to a network in VHI and you're prompted with the message:

Only single subnet with IPv4 is supported. (BAD REQUEST) (Request-ID: req-11ccf193-9c99-4dcf-b936-44fab3d6a1ff)

Workaround

1. Login to primary node

source /etc/kolla/admin-openrc.sh 

Your primary node, is_primary = True

[root@vhi-node1 ~]# vinfra node list
+--------------------------------------+--------------------------+------------+-----------+-------------+----------+
| id | host | is_primary | is_online | is_assigned | is_in_ha |
+--------------------------------------+--------------------------+------------+-----------+-------------+----------+
| 15e3bd8d-a134-5220-60e4-9f3ed99f1b43 | vhi-node1.vstoragedomain | True | True | True | True |
| 69e57ec1-c40a-8b7a-b16a-b3485324ee22 | vhi-node3.vstoragedomain | False | True | True | True |
| d6fe4fb2-6f1c-78c1-e847-78be02db375e | vhi-node2.vstoragedomain | False | True | True | True |
+--------------------------------------+--------------------------+------------+-----------+-------------+----------+

2. Add a subnet using the OpenStack command:

Replace value in < > accordingly which suite your setup.

openstack --insecure subnet create <subnetname> --network <networkname> --subnet-range <the ip/range> --gateway <yourgateway> --allocation-pool start=<startIP>,end=<endIP> --dns-nameserver <DNS_IP_#1> --dns-nameserver 
<DNS_IP#2>